As a conventional method for separating and collecting an optically active amino acid amide, for example, a method is suggested, which comprises asymmetrically and enzymatically hydrolyzing a racemic amino acid amide to prepare an aqueous solution containing an optically active amino acid amide and an optically active amino acid; adding an organic solvent that is a readily-soluble solvent for the optically active amino acid amide but is a poor solvent for the optically active amino acid to the obtained enzymatically reacted solution or a concentrated product thereof to precipitate the optically active amino acid; and separating the optically active amino acid amide contained in the organic solvent phase (see Patent Document 1, for example).
However, when the above method is applied to an aqueous solution containing not only the optically active amino acid amide and the optically active amino acid but also an acid, base or salt which is originated from the raw material for the amino acid amide or an aqueous solution of microorganism cells or enzymes used as catalysts, a problem occurs such that yield or chemical purity of the optically active amino acid amide is deteriorated because even after the addition of the organic solvent which is readily-soluble for the optically active amino acid amide and poor for the optically active amino acid to the obtained enzymatically reacted solution or a concentrated product thereof, the optically active amino acid amide to be soluble and the optically active amino acid to be insoluble are not properly charged electrically, thereby decreasing the content of the optically active amino acid amide in the organic solvent phase and allowing contamination with the optically active amino acid.    Patent Document 1: Japanese Patent Laid-Open No. 2001-11034